A cubic crystalline powder sample is irradiated with the radiation from a X-ray tube with a copper anode. A Geiger-Mueller counter tube is automatically swivelled to detect the radiation that is constructively reflected from the various lattice planes of the crystallites. The Bragg diagram is automatically recorded. A graphical evaluation procedure is used to assign the reflexes to the individual lattice planes and to determine the corresponding Bravais lattice type as well as the lattice constant of the substance.

Tasks

1. Record the intensity of the Cu X-rays back scattered by a cu-bic powder sample as a function of the back scattering angle.
2. Assign the Bragg reflexes to the respective lattice planes. Determine which Bravais lattice type it has.
3. Calculate the number of atoms in the unit cell.

Learning objectives

• Crystal lattices
• Crystal systems
• Bravais-lattice
• Reciprocal lattice
• Miller indices
• Structure factor
• Atomic scattering factor
• Bragg scattering
• Characteristic X-rays
• Monochromatization of X-rays